Configure the option "Wrap text to window (in continuous and outline view)" (Tools > Options)

Here you can configure if TextMaker breaks lines at the window border, instead of formatting the lines for the printed page.

Supported on: At least Windows Vista
Registry HiveHKEY_LOCAL_MACHINE or HKEY_CURRENT_USER
Registry PathSOFTWARE\Policies\SoftMaker\TextMaker 2016
Value NameWindowWrap
Value TypeREG_DWORD
Enabled Value1
Disabled Value0

softmaker.admx

Administrative Templates (Computers)

Administrative Templates (Users)