Easiest but temporary solution is this.
Go to koreader folder, then frontend/apps/reader/modules/readerdogear.lua.
Find this line (around line 77 on current nightly -2024.04-186):
Code:
local new_dogear_size = math.min(self.dogear_max_size, math.max(self.dogear_min_size, margin))
Add a multiplier after the equal sign, something like:
Code:
local new_dogear_size = 3*math.min(self.dogear_max_size, math.max(self.dogear_min_size, margin))
For example, I multiplied by 3, you can choose the one that fits you.
Solution is temporary, because after update you would need to do this again.
Unless someone can make a user-patch for that...