I passionately believe there are one or two solutions.
The most obvious solution is to sell your cargo first before you go to the manifest screen. You certainly have noticed that your cargo manifest takes roughly one half of the screen if you have various commodities in your hold, which automatically leaves only the other half to display all the other stuff. Reduce the space needed for your cargo manifest, and everything else gets more space.
In whatever controls the page switching over to display more equipment if the script can be adapted to allow for overflow that would keep going through the pages till it reached the last entry like when you do it for your installed equipment.
As Kaks already hinted at in his answer, this has nothing to do with script. In order to implement a scrolling solution of any kind, the code of Oolite
has to be re-programmed. This has already been done for the status screen, which also was overflowing until Oolite 1.73. Unfortunately the code for displaying screens is a mess, therefore the arrows implemented in a couple of screens (status, equipment, shipyard) cannot
be transferred to other screens (manifest). Everything has to be re-written from scratch. As Kaks pointed out, there is currently nobody in the development team with enough time/energy at their hands for doing that.