Translation Manager comes with support for all the core Umbraco text-based property editors, as well as most of the popular 3rd party text-based property editors. However, there may be times when you have custom property editors that are not covered by the core installation.
Translation Manager 8.3 and above
If your custom property editors store text in the same way as any of the built-in editors, then you can map that editor value by using the custom mappings section of the
<add key="MyCustomTextProperty" value="Umbraco.Textbox" />
<add key="MyCustom.Editor" value="Umbraco.TinyMCE" />
If you custom mapper is also used in the grid you should also add a Umbraco.Grid.[name] mapping. To cover those situations. e.g.
<add key="Umbraco.Grid.MyCustomTextProperty" value="Umbraco.TextBox" />
You will be able to see whether you custom mappings have loaded on the Translation Manager Diagnostics tab.
These custom mappings will also be used for link mapping, so if you have any controls that include links, you can use these mappings to catch those values.
<add key="MyCustom.LinkMapper" value="Umbraco.MultiUrlPicker" />
Versions before 8.3
Prior to v8.3 you can map custom text properties using the mapper / text settings.