Use shortcut.dat in order to assign shortcut keys to menu by plug-in function in the same way as regular method. See shortcut.txt in the Data folder for shortcut.dat itself.
Select menu [Help] [About Plug-ins].
Add the following line, for example, to shortcut.dat referring 3 values of ProductID, PluginID, and Index.
T c P 56a31d20 5eac34e0 0
By this operation, Ctrl+T is assigned to the shortcut key for [Create Text].
Supplementary:
The first two letters, "T c", mean the assigned key, Ctrl+T and the third
letter, "P", means plug-in. And the remaining 3 letters respectively become ID
of plug-in.