Tagged the wide sidewalks as bicycle=yes, since the eastbound Cathcart Way bike lane has a ramp up to the wide sidewalk just before 148th St SE. These "wide sidewalks" seem to be a common tool used by governments and developers to avoid building real bike infrastructure. They call them "shared use paths", but the reality is they're engineered exactly like a normal sidewalk and come with all the usual downsides of biking on a sidewalk.

Portion north of Silver Lake Water and Sewer District building is owned by a HOA, but there's no signage prohibiting access and it seems to be well used. Thus, I marked that portion as "permissive" access.

I stopped by there today and confirmed it is still a school street and the signage is as I remembered. Here are some photos of it: https://www.flickr.com/photos/204891673@N04/albums/72177720335246930

I'd be very surprised if the school street designation were removed, but I'll check and report back next time I'm over there. If I recall correctly, the street had semi-permanent chicanes installed with a "street closed / local access only" sign at either end.

To view WA DNR LIDAR imagery in iD: @jake-low/diary/397224

bicycle, foot, horse - access tags on members
cycle_network - removed US:PTC, as they only manage one trail (this one)
description - didn't provide any information not already present in other tags
note - this field is supposed to be used to provide context for editors
surface - surface tag on members
usage - nonstandard usage of tag
wheelchair - retained on walking route

Just for reference, the original relation was changed from route=bicycle to the multi-value route fairly recently: changeset/171014206 (11 months ago, with the relation being 14 years old).

Reverted in changeset/186250522

In changeset/186161061, I created a separate route=bicycle for the ODT and added the route=bicycle;foot;inline_skates;horse one (relation/1896877) to it as a member. I was hoping that this would allow it to show up on cycling maps like OpenCycleMap or CyclOSM, but it doesn't. Will look into other options to achieve this.

Created a separate route=bicycle for the ODT so that it hopefully shows up in OpenCycleMap and CyclOSM, the two cycling maps most prominently displayed on osm.org/. The main ODT relation (relation/1896877) is tagged route=bicycle;foot;inline_skates;horse, which is recognized by few renderers. I do not consider my new relation a case of osm.wiki/Tagging_for_the_renderer. To quote that wiki page: "Using correct tags to get something rendered is good, using tags mismatching reality to get something rendered is bad."

Tagging the road with bicycle=yes would be fine, but unnecessary because all roads in the area allow cycling by default.

The bicycle=designated tag is for roads or paths that have signage indicating the road/path is intended for cycling. In this area, such signage is rather rare on roads—the only examples I can think of off the top of my head are Seattle's Healthy Streets.

There are yellow diamond signs with a bicycle symbol on this road. A yellow diamond sign is a warning sign to inform road users of a potential hazard. In this case, the signs are there to warn drivers that cyclists may be present, because the design of this road puts cyclists at risk. This is distinct from a sign indicating the road is intended for cycling.

The entire road has a shoulder, but it varies from 7' to less than 1'. In the absence of any guidance on the OSM wiki, I chose 4' as threshold for cycleway=shoulder. Per WSDOT, this is the minimum width of a shoulder that "facilitates bicycle travel", though their recommended minimum is 5'. This jives with my subjective experience cycling: 4' can be pretty uncomfortable to ride on and provides little margin for error, but it's wide enough that you'll have room to maneuver around small obstacles on the shoulder.

Source: osm.wiki/Contributors#City_of_Shoreline,_Washington, Local Knowledge, Aerial Imagery

Source: osm.wiki/Contributors#City_of_Shoreline,_Washington, Local Knowledge, Aerial Imagery

Source: osm.wiki/Contributors#City_of_Shoreline,_Washington, Local Knowledge, Aerial Imagery

Source: osm.wiki/Contributors#City_of_Shoreline,_Washington, Local Knowledge, Aerial Imagery

Sources: osm.wiki/Contributors#City_of_Shoreline,_Washington, Local Knowledge, Aerial Imagery

Source: osm.wiki/Contributors#City_of_Shoreline,_Washington, Local Knowledge, Aerial Imagery

Source: osm.wiki/Contributors#City_of_Shoreline,_Washington, Local Knowledge, Aerial Imagery