No, you can't.
(We created the merging feature mostly because when we started the maps, we imported all destinations from a previous "travel log" feature as individual trips, and wanted to allow people to swiftly merge them together into distinct trips (as we didn't trust ourselves to guess right and do that automatically). Never really considered the need to split a trip into distinct parts, and as far as I can remember, this is the first time it's been requested. Might be that it can be taken into consideration for the next version of the maps feature, though...)
Thanks Sander for the swift reply.
Its been on my mind for years and maybe others had wondered about it. Could as I've mentioned, set up polls to see who merges/uses map page.
I would like to see all my destinations and currently I have to select one trip then via scroll down select "All trips" maybe that can also be made automatically available with my created trips page (the page where you tick which ones you would like to merge?
If I do tick to merge all, do I still have the original trips as separate maps?
If you merge them, they will all become one big trip. Not at all what you want from what I gather.
The view to see all your trips together is http://www.travellerspoint.com/member_map.cfm?user=boulderman
There is a link on your profile to "All trips by boulderman". That will lead a visitor to see all your trips together.
I should add, we are in the middle of developing a major upgrade to the maps, so if there are interface issues like this that are bothering you, just hold tight for a while and see what you think of the new version first - there are a lot of improvements.