How can I delete multiple activities more quickly?

[xing]

I have a very large dataset, say more than 5000 activities. I have misplaced activity tags for around 3000 activities, so I want to delete these 3000 activities or just delete all activities and re-import all of them. How can I make it works instead of
1) creat a new .fet file from scratch
2) select the first activity, click remove, and long pressing the Enter button
both of them are time-consumiing.
Is it possible to add a "Delete/Remove/Clear all" button in the further version?
Many thanks for any suggestions.

[Liviu Lalescu]

You can remove all the activities:

1) From the Advanced > Activity planning;

2) Open the XML fet file with a text editor and remove the section between <Activities_List> and </Activities_List>.