You can make variants of your base letters with suffixes like .topAccent or .bottomAccent, then this letter will be preferred for generating compounds with marks that make use of the indicated anchor.
I know, sounds complicated, so here is an example. Say you have a lowercase g with a funky ear. Very nice, but it may get in the way of top accents in compound glyphs like gcommaaccent, gcaron or gdotaccent. So you can duplicate your g, name it g.topAccent and flatten its ear, perhaps like this:
The next time you create a g composite that has a top-connecting mark, say gcircumflex, the .topAccent variant will be preferred for the base:
One base letter for multiple anchor types
You can also combine multiple anchors in one such suffix. Make sure the names of the anchors are:
- written without any spaces in between,
- camel-cased, and
- in alphabetical order.
Good examples: .bottomTopAccent for bottom and top anchors, .bottomOgonekAccent for bottom and ogonek anchors, or .hornToprightAccent for horn and topright anchors. Easy.