You can merge nodes, fields or tags in Tana by putting the references below each other, selecting them, and choosing merge nodes. Below is an example of two tags, two fields, and two nodes below each other. Note that you should not have a node with a tag, or a field, but the actual tag, or the field definition - you can find both in the @-mentions menu.
A few other things that can be worth knowing if you need to rework a setup in tana:
The Set command lets you apply field values to any number of nodes in one go.
Search nodes can be converted to plain lists via the command line. This will simply detach the search expression, and leave the results as see them – and the list can now be manually edited.
The “Bring referenced node here” command lets you change the ownership of nodes to the current context.