Not sure if people will think this is obvious or not - but there is a slightly quicker way to re-insert abeam points than using the fix page/abeam point method (if you already know it, stop reading) which is the way I was shown to do it. This way saves you leaving the Legs page and is much quicker.
EG if you are direct VATON and want to put AVANT in as an abeam point (for an altitude or speed restraint, or just for fun)... In the legs page type AVANT in and put this in line one. Then put VATON on top of AVANT in line one, select abeam points and execute. Hey presto, new abeam point without having to leave the Legs page.