You can load multiple track sets at once, but only in case they do not overlap. The later means you can't load multiple configuration track sets for one track - they always overlap. In case you have no Internet access on site, there is a possible workaround:
For each configuration you want to have with you:
1) While in a WiFi, load the track set.
2) Goto Lap List ‣ this track set ‣ Certified Track Set
3) Select one Information POI and change something (e.g. a corner name)
4) This will make this certified track set a user track set
5) Select the Certify function usually used to submit user track sets for certification
6) Rename the mail generated to have the certification's name in the subject
7) Change the To name from Tracks@gps-laptimer.de
to your own email address
8) Send the mail to yourself
Once this has been done, you will have a mail fro each configuration in Mail. You can open one of it and touch the .hpoil file to install it in LapTimer without Internet connection now.
I'm aware this is a inconvenient workaround, but at least it works.