I use the following method to save new LibreOffice files to the local area network using LibreOffice version 6.0.7.3 This method uses the File>Save Remote… option.
On selection of the Save Remote… option, a Remote Files dialogue window presents with a list button to Add Service for a network share. I left click on the Add Service button which then displays a File Services dialogue window that contains a drop down list for Type.
The drop down Type list on the File Services window allows me to select window’s share for Type after which the File Service dialogue window expands to include fields for a Host computer and share name.
For the Host field, I specify the name of my NAS storage device and in the Share field, I enter a share name (I have only one) defined on that device. I also put the share name in the label field (optional) presented on the File Services dialogue window and then click the OK button. I don’t specify a User or password because I deliberately set Samba up on the NAS box to work with anonymous connections (I like it that way).
On the ensuing Remote Files dialogue window, I’m presented a tree diagram of the network share I supplied earlier. In the left pane, I can drill down to the desired directory and then specify what File name to use to save the file when I click the save button.
The intuitive solution to use File>Save>Other locations option just didn’t seem to work initially. I could not navigate past the share name presented when I selected the remote computer displayed with the Other Locations option. I would get an error indicating “Could not read the contents of Share_Name”, “Not a directory.”
However, after I added the service using the Remote Files dialogue, that service then appeared under other locations allowing me to save files via the Files>Save>Other Locations option by selecting the service.