in QGIS 2.18 I used the table manager plugin for renaming or removing columns in a table. This plugin doesn´t exist in QGIS 3.4.1.
Is there any other plugin or way to rename, remove or order columns in the attribute table of a vector layer?
Try the Refactor Fields tool in the processing toolbox.
You can rename, reorder, and change the types of the fields. You can also import fields from other layers and map the old fields to the new fields.
It creates a new layer but if you want you can just save over the original.