"Other Activities" ribbons ribbon enable rule

Hi, all.

I am using MS CRM 2016 on-Premises. I am customising Activity entity ribbons, making custom enable rules.
In the split button "Other Activities" there are some ribbons of creating different custom activities, for example message1, message2 e.t.c.
But when I am opening the entity in RibbonWorkbench - the "Other Activities" split button is empty, it contains no controls.
I guess - custom activity controls are generated at runtime.
Is it possible, to add enable rules to custom activity creation ribbons?

thank you.
With regards, Yuriy.