This is a VERY useful function (Arrange Window, Functions > Objects menu), especially with audio sequences. It allows you to "butt" the start of one sequence against the end of the previous one. So, select 2 or more audio regions in the Arrange Window and use this function. When the regions are end to end, you can use the glue tool to create a new file from your edits ("Digital Mixdown" from the Arrange window's Audio menu does the same).

With MIDI sequences, the first sequence will retain its position and the sequences that follow will move end to end.