Not used the program in years anymore at this point, but AFAIK you could just define them like this:

<Hotkey ScrollLockon Alt MainKeyList>
<SendLabel f1, f2>
<Key %Trigger%>

<Hotkey ScrollLockon Ctrl MainKeyList>
<SendLabel f1, f2>
<Key %Trigger%>
This of course uses your MainKeyList so in theory at least it gives you modifier options for all keys defined in it. I guess you could just do it similar to this as well.

<Hotkey ScrollLockon Alt 0-9>
<SendLabel f1, f2>
<Key %Trigger%>
Take this with a grain of salt OFC since I'm not able to test this currently.