There's nothing macOS-specific about this.
I tried, on Ubuntu 18.04, the 2.6.10 in the standard 18.04 Wireshark package, and Statistics > Resolved Addresses pops up a text window that can be copied and pasted.
A version I built from recent master-branch source, however, has a table, with no easy way to copy and paste or to save to a file.
You should request some mechanism to save resolved addresses by posting an enhancement request on the Wireshark Bugzilla. Note that there's "saving all resolved addresses to a file", which would produce a file not directly usable as a hosts file or an ethers file or..., and there's "saving all resolved {IP,MAC,IPX,...} addresses to a file", saving only one type of address to the file, which would produce a file of that sort but wouldn't save all addresses.
https://osqa-ask.wireshark.org/questi...
It would be a multi step process but the data is available in the PCAPNG Name Resolution Block.
View -> Reload as File Format/Capture
Expand
PCAPNG File Format
then look for theName Resolution Block
.Right click on it then
Expand Subtrees.
Right click
Block Data
thenCopy -> All Visible Items
Paste into text editor.
Maybe someone else comes up with a prettier, simpler method.
Forgot to add, "Mung as needed" once it's out of Wireshark. :-)
Note that you may have to save the file first before doing View -> Reload as File Format/Capture; if, for example, you do a live capture, the file was written by dumpcap, and dumpcap (by design!) doesn't resolve host names and thus doesn't write out a Name Resolution Block. In addition, if the file isn't a pcapng file, it won't have a Name Resolution Block to see.
I.e., there really isn't a good way to do this, but there should be, so getting bug 16419 fixed is the ultimate answer.