Can I use the Fund Allocation Solver on multiple plans at the same time?

Yes you can.

There is a button at the bottom of the page 'Change funds on multiple products' which has options such as 'Add funds', 'Import a model portfolio' and a number of others.

This will enable you to choose the plans that you want to edit funds on, complete the work on each plan and then come back here to use the option 'Use fund allocation solver'.

What each item does within the 'Change funds on multiple products' button does is covered in a separate article.