Automagic Forum

Organising my flows, I have lots of them related with one topic in a folder. Some are related to a specific aspect of that topic, and some with another. Therefore, I advice to add sub folders for a better organization of the flows.

Though I can't help you with subgroups, I recognise the problem. What I do to reduce the impact of too numerous flows is to use multiple trigger flows, thereby combining several flows into one.
Inside the flow I check what trigger caused the flow to execute, and branch accordingly. So these flows often have an expression condition, saying something like:
startsWith(trigger, "...")
In addition to reducing flow count, this approach also helps with editing flows, as related actions and conditions can now be found in the same flow. As consequence, it happens less frequently that I must close one flow, in order to open another for editing. I'm afraid that subgroups, by need of additional navigation, will only make that worse. An alternative solution may be, if ever implemented, to allow several unrelated triggers in one single flow, each initially with its own control flow path.