I haven't made sense of the way the activities sort for the Harmony 700, but I've found how to force it to show activities in the sort order I want using the desktop software. Assume you want item 1 to be Watch TV, item 2 to be Watch Chromecast, item 3 to be Watch DVD. Do the following:
1) In the desktop software create three activities -- it doesn't matter what three you create or what equipment is associated with them because you're going to change them later.
2) Sync the remote with those three activities.
3) Check the remote and write down the sequence that the activities now show on the remote itself
4) Go back into the software and edit the activity that showed as the first activity on the remote itself. Change its settings/devices per the activity you WANT to be the first activity on the remote (per my example, Watch TV). Save that.
5) Using step 4 as your example, do the same for the second and third activities, as well.
6) Sync -- now you will find that the activities you WANT to be items 1, 2 & 3 on the remote itself ARE items 1, 2 & 3.

I've confirmed this works, and it should work no matter how many activities you want on your remote. Should you finish the above and later decide to add ANOTHER activity -- be warned, you may have to go through the above steps for one or more of your activities depending on where the NEWEST activity shows up on the remote itself.