[jcn363]

Originally Posted by Martina Schein

Enclosed the desired screenshot. As you can see, the distances above and below are quite large. With the firmware versions before, they were about 2 mm.
In the file Kobo eReader.conf I entered this under the section [Reading]:
fullScreenReading=true

This is the cleanest I can figure it right now.

FOOTER
Select show footer into settings.
BE CAREFUL NOT TO CHANGE THE LENGTH OF THE REPLACEMENT STRING.
You can increase red color text.

Spoiler:

  - FindReplaceString:
      Find:    "ReadingFooter {\n  qproperty-footerMargin: 105;\n}\n\
                ReadingFooter[qApp_deviceIsDragon=true] {\n  qproperty-footerMargin: 170;\n}\n\
                ReadingFooter[qApp_deviceIsDaylight=true] {\n  qproperty-footerMargin: 221;\n}\n\
                #caption[qApp_deviceIsTrilogy=true] {\n  font-size: 19px;\n}\n\
                #caption[qApp_deviceIsPhoenix=true] {\n  font-size: 23px;\n}\n\
                #caption[qApp_deviceIsDragon=true] {\n  font-size: 29px;\n}\n\
                #caption[qApp_deviceIsAlyssum=true] {\n  font-size: 32px;\n}\n\
                #caption[qApp_deviceIsNova=true] {\n  font-size: 32px;\n}\n\
                #caption[qApp_deviceIsDaylight=true] {\n  font-size: 37px;\n}\n\
                #caption[qApp_localeName=\"ja_JP\"] {\n  font-family: Sans-SerifJP, sans-serif;\n  font-style: normal;\n}"
      Replace: "ReadingFooter{ qproperty-footerMargin: 00; min-height: 40px; max-height: 40px; }\n\
                ReadingFooter[qApp_deviceIsDragon=true] { min-height: 00px; max-height: 00px; }\n\
                ReadingFooter[qApp_deviceIsDaylight=true] { min-height: 60px; max-height: 60px; }\n\
                #caption{ font-size: 16px; margin-top: -08px; }\n\
                #caption[qApp_deviceIsPhoenix=true] { font-size: 20px; }\n\
                #caption[qApp_deviceIsDragon=true] { font-size: 26px; }\n\
                #caption[qApp_deviceIsAlyssum=true], #caption[qApp_deviceIsNova=true] { font-size: 30px; }\n\
                #caption[qApp_deviceIsDaylight=true] { font-size: 32px; }\n\
                #caption[qApp_localeName=\"ja_JP\"] { font-family: Sans-SerifJP, sans-serif; font-style: normal; }   "

HEADER
If you have activated

  src/libnickel.so.1.0.0.yaml:
    Custom kepub default margins: yes

you can reduce

Spoiler:

  - ReplaceZlib:
      Find:    "#StatusBarView[qApp_deviceIsTrilogy=true] {\n  max-height: 71px;\n  min-height: 71px;\n}\n\
                #StatusBarView[qApp_deviceIsPhoenix=true] {\n  max-height: 91px;\n  min-height: 91px;\n}\n\
                #StatusBarView[qApp_deviceIsDragon=true] {\n  max-height: 121px;\n  min-height: 121px;\n}\n\
                #StatusBarView[qApp_deviceIsDaylight=true] {\n  max-height: 157px;\n  min-height: 157px;\n}"
      Replace: "#StatusBarView{max-height:60px;min-height:60px;}"

perhaps to

  - ReplaceZlib:
      Find:    "#StatusBarView[qApp_deviceIsTrilogy=true] {\n  max-height: 71px;\n  min-height: 71px;\n}\n\
                #StatusBarView[qApp_deviceIsPhoenix=true] {\n  max-height: 91px;\n  min-height: 91px;\n}\n\
                #StatusBarView[qApp_deviceIsDragon=true] {\n  max-height: 121px;\n  min-height: 121px;\n}\n\
                #StatusBarView[qApp_deviceIsDaylight=true] {\n  max-height: 157px;\n  min-height: 157px;\n}"
      Replace: "#StatusBarView{max-height:35px;min-height:35px;}"

Beware because it's the menu bar size too.
Good luck.