Cmd-A selects all global guides. It should take filters into account and only select the ones that appear in the current glyph layer.
The current behaviour isn’t very obvious and it causes some headaches when trying to set up global guides with different filters. One mistake (Cmd-A, change filter settings) and suddenly all the global guides with various filters have been overridden and moved into the same category.
I would propose to completely get rid of selecting all guides in the select all command (cmd+A). The amount of times I have deleted guidelines since it was introduced is ridiculous. I think it’s one of the worst features on the app.
What exactly is the issue? It is a separate step in the select-all cycle, like hints, like paths, like components, etc. Deleting something when it is selected would be an issue with any selection, not just guides.
And you can lock guides. That excludes them from selection.
The reason is that it makes me make mistakes (alt+A and then delete) and then there is no undo. Locking/unlocking is an option but it’s not optimal imho. It should be removed like it was in the past. Some people may find it useful. I find it horrible and useless in my workflow. Perhaps make it an option in the preferences.
You can’t undo them if it happened in the background. I copy a shape in the background. I make edits in the frontground. I switch to the background and cmd+A and delete. If the outline was already selected (for whatever reason) and I do the process too fast to think about it, the global guides are selected, deleted, and gone bye bye.
I’ll repeat my position. Make it an option. It certainly is not working for everyone the way it works for you.