In learning ACT, I've experimented with some 12 different layouts set up under different tabs, which has taken me weeks of time. I long to be able to move parts of a layout ready-made onto another layout. But as all layouts are independent of one another, this cannot be done.
Here's how this could be done.
Change the status of FIELDS TAB, which is there by default when ACT is installed, to be the same as
i.e. FIXED and CONSTANT regardless of which layout is selected.
But when it is selected to display, alongside the other core tabs, there is only the one layout on it. The user can of course alter the layout ad infinitum, but whichever layout is selected, that same FIELDS TAB will display the same fields, across all layouts.
Then, when setting up other layouts, any fields from the top part of the screen can be dragged down to the FIELDS tab, and dragged back up again when another layout is selected.
Likewise, fields on user tabs, can be dragged up to the top part of the screen, then back down to the FIELDS tab when another layout is selected.
So the FIELDS TAB would then function as a LAYOUT SNIPPETS tab. When not designing layout, the tab could be deselected, so it did not appear on any view.