If you are simply trying to show, for example, that your personal preference is to have a short press of "Stop" stop the VCR, and a long press of "Stop" eject the cassette (an LKP I personally use), I assign the "short" function to the button directly, and the "long" function to the x-shifted button (which is, after all, just a fancy way of giving a name to an otherwise "phantom" button). I do this IN THE RM UPGRADE.
Then I build the LKP on "VCR/Stop" in IR as follows:
Short=shift-Stop (uses shift-cloaking to access the "underlying" Stop function);
Long= x-shift-Stop (executes "eject")
or, to put it more generically, in RM:
Assign "short" functions to the primary button, and
assign "Long" functions to the x-shifted version of that button.
Put a note in the upgrade "notes" section stating this is how you structure the LKP function "partnerships" in IR, i.e. wherever you have an "x-shifted" button assigned as a keymove, you access it via an LKP.
Meanwhile, you have the two functions you want "sharing" one button clearly assigned to that precise button in your RM upgrade.
Of course, you still have to BUILD the LKP in IR, but the relationship between the two functions you describe is shown and explained in your upgrade file with a SINGLE NOTE, rather a bunch of notes trying to connect various phantom button assignments with various other function assignnments as "partnered" via LKP.
Another example where I have used this technique is with a CD changer, where number function "X" is assigned to the corresponding basic number button, and the "disc X" function is assigned to the "x-shifted" number button. Then the LKPs are trivial to build in IR, as the "special relationship" between the two functions associated to one button is already predefined in the imported RM upgrade.
Of course, this presumes you're using the extender. Otherwise, the "x-shifted" column of buttons won't appear in RM
But since this post is in the "extender" section, and MOST LKP protocols are designed to work only with extenders, I think I'm on safe ground here assuming that. 8)
P.S. Before the advent of RM, in which you can predefine keymoves to "x-shifted" buttons, I did this in KM, but had to use only "shifted" rather than "x-shifted" buttons, so that created an extra hassle in IR where I had to take every imported "shifted" keymove from the KM upgrade that I wanted to do this on, and edit it in IR to be an "x-shifted" keymove.
