What could I replace the gui values with to still make it work properly then?
You'll replace it with actual numbers. You can make a new project with the default Ren'Py template and copy over the actual values of any gui value that shows up if you aren't sure. Something like
background Frame(["gui/frame.png"], gui.history_frame_borders, tile=True)
can just be
background Frame(["gui/frame.png"], 5, 5, 5, 5, tile=True)
There isn't really much use of the gui values in that code so you should be mostly fine to copy it over.
Looking closer, this code relies on the default layout of the history screen and the provided styles. The template styles use an hbox rather than a window + name label positioned individually. It'll be easier if you just adjust the existing code and modify it how you like. For example, you can modify the first few lines of the history screen:
screen history():
tag menu
## Avoid predicting this screen, as it can be very large.
predict False
# add HBox(Transform("#292835", xsize=350), "#21212db2") # The background; can be whatever
# use game_menu(_("History"))
frame:
align (0.5, 0.5) xysize (1450, 900)
textbutton _("Return") align (1.0, 1.0) action Return()
viewport:
mousewheel True draggable True pagekeys True
scrollbars "vertical" yinitial 1.0
has vbox
style_prefix "history"Make whatever adjustments you like to the sizes of everything.