Not sure if this is common knowledge,but i dont think so. We can resize our inventory and its pretty simple
Open your pokemmo folder -> data -> themes -> default -> ui
and open the file named Inventory.xml with notepad or something similar
on line 28 and 29 it says:
<param name="minWidth"><int>430</int></param>
<param name="minHeight"><int>278</int></param>
you can change the numbers "430" being the width of your inventory and "230" being the height. and then just save the file and open up the game.
Im using:
<param name="minWidth"><int>430</int></param>
<param name="minHeight"><int>500</int></param>
this is how it looks like btw
you cant increase the width too much, if you can at all. the inventory will become bigger but it'll just be empty space. the Height you can increase as much as you want iirc...