pressing the Opt key does not do any tool switching
you can temporarily switch to a different tool with the Cmd key (Edit) or space bar (Hand) or Ctrl-Opt-Cmd (Measure): in Glyphs 3, the temporary tool will be indicated in the tool bar, but not in Mini (I believe this is what you meant?)
a tool icon that holds multiple tools, can switch through the tools either by clicking and holding, or by Shift+shortcut key; e.g. Shift-V will switch between Lasso and regular Select tool. In Adobe Illustrator you can switch through a tool stack by Opt-clicking on it (perhaps you meant this?) but not in Glyphs.
I am totally new to Glyphs so maybe I was doing something wrong.
I just wanted to do a “Paste special” to replace certain glyphs (latin base and latin west Europe). However I copied the glyphs one by one…
Let me say that Glyphs looks fantastic! Loving this app on Mac!