Hi after getting a momo a couple of weeks ago I have figured out after several hiccups how to get more space, Need to partition your extsd card using either a phone with recovery menu called cwm and there is an option in advanced or do on pc. Minitools is good. Resize partion then turn unused space into EXT 4 , for me I have 4 gig ext and 26ish on external sd instead of 32. But you can change to whatever needed. Install superuser from store then open, click i on toolbar then click where says check update and install latest binary, important I found, Then install linksd, On first run you need to grant superuser access. It will if it finds your 2nd partition bring up option now choose the ext 4 option which you formatted the sdcard partition to, will tell you to reset, after reboot should be done to test reload link2sd goto storage info in menu options and you should see extra drive in info now.
In settings turn on autolink check all options about linking, scroll down change native install to internal from automatic, You can click buttons on top right and sort by system apps user sd internal ect. Do mutiselect on user apps and create link, you should save loads of space if you have installed apps already. S2e does not work unfortunately which is easier to use,
There is an external to internal app in store which I almost got working but didn't, would be ace if it did though. Hope this helps sorry I'm not a writer haha