Hi there !
Let me ask you this little question. I´m trying to reduce the faces from High Poly to Low Poly to an already shaped low poly object (I need to make it on paper, via Pepakura). This stl file has 366,318 faces in Blender (v 2.80.75) and has an already low poly shape. I used Blender to make Decimate Collapse to a 1000 faces (I exported this reduction in a new stl file) and then, little Planar reduction and from then, I manually deleted the excess edges and the low poly shape came out (I imported the stl file with the 1st. reduction and then made the editing). But, but, but ALL THE EDITING CHANGES WERE NOT SAVED, just the first Collapse reduction (of course, I exported the imported stl when the low poly shape on the screen, after editing it, was perfect).
So, the Tris to Quads, the Mesh symmetrize, Planar reduction, manual edge dissolving and others editing instructions do not get saved. I searched for a "freeze faces" command or something similar, but I don´t know what I am doing wrong or if it is an error from the stl file (which I did not model).
So, please a little help! Thank you for reading and for any info you can provide.