Modify refund and relocation cost amounts in-game, remove time limit for refund. Source
You can change all the settings in-game, except enabling/disabling time limit.
The configuration file is …SteamSteamAppscommonCities_Skylinesrefund.settings.xml, changeRemoveTimeLimit to true to disable the time limit.
OnlyWhenPaused setting modifies the default behaviour; if enabled and the game is paused, you won’t get a refund even if the time limit hasn’t been reached.