assigning variable in trigger wizard

When I am using multiple variables, I am sometimes unable to find variables I know exist but are not accessible in the scrolldown window.  I am only able to scroll up or down so far and this range doesn't include all the variables I've created. Sometimes I am able to type the first two letters which then populates the trigger window but sometimes this trick doesn't work.  Other times I have to rename a variable with an X in front of it which seems like a dumb workaround but it works

I've read that there is a very high limit to variables but once I get into fifty or more, this is always an issue for me.  Anyone else have this 'missing' variable issue?