The Insert Time window allows to insert blank space in the timeline, on the selected track(s). It is accessed through the Track > Insert Time menu.
The Insert Time window not only allows to set the time inserted, but also some fine tuning options:
Both the two time fields have a useful context menu, that allows to copy/paste the time and change the display among one of the clock modes. The Insert Time field also has two options to Set from Playhead (to get the insertion time from the playhead, which is what happens by default) and Locate to This Time which moves the playhead to the time field value, useful if the field has been manually edited to better visualize the insertion point.
By default, inserting time only results in shifting positions of the regions beginning after the insertion point. The "Inserted regions should" dropdown menu allows to choose what happens to the regions that exist at the insertion time :
This last mode allows a brute force insertion, creating a blank space in all the selected tracks, and replacing multiple operations.
Note: One interesting option is, if a range selection (created with in Range Mode) exists, it is used as the default parameters in the window, instead of the playhead, for both the start time and duration.
The Remove Time window, accessed through the Track > Remove Time menu, is very similar to the previous, and its options are very similar. Only the "Inserted regions should" option is not present
The range selection note above can be especially useful in this context.