I cannot confirm that Firefox 78.0.1 provided by Linux Mint does not permit to add additional search engines.
Means that I can confirm that adding additional search engines on Fireofx 78.0.1 may work.
At least here on LM 19.3 with Firefox 78.0.1 (78.0.1+linuxmint1+tricia), I succeeded in adding Google and Bing.
I admit I did not try more engines than those 2; and I have removed Bing again later on.
(Though the latter operation is irrelevant for the reported problem.)
1. Prerequisite for adding to work:karlchen at 20:00 CEST wrote:No need to follow the steps below, there is a better and more straight forward way.
See xenopeek's post below.
The steps given by me do work. But they are more complicated than necessary.
Under Preferences => Search, the separate search bar must have been enabled. (marked in screenshot)
User sueede had already mentioned so in his post above.
2. Adding a search engine:
- Go to Preferences => Search. Below the list of One-click Search Engines click on the link Add more search engines.
- Doing so will opem a new browser tab amd take you here: Search engines in Linux Mint.
- Click on an icon of a search engine, which is not already in your list of One-click SearchEngines.
I will click on Bing.
- Doing so will take you here: Bing in Linux Mint
- The last line on this page tells you: Click here to add Bing to your search engines.
- Clicking on the word and link here will do precisely nothing.
Clicking on the little white plus in the green circle (cf. screenshot below)
will make the "Add Bing" line appear (cf. screenshot)
- Click on it.
As the next screenshot illustrates Bing is now listed as one of your search engines.
- Switch back to the Preferences => Search tab. It should list "Bing" among your One-Click Search Engines now.
- Goal achieved.
- I have not found a way of making this work without the separate search bar next to the address bar. - I am sure it should work.
As I could not find an existing report on Github, this one has been submitted: Firefox 78.0.1: adding 1-click search engines only works, if separate searchbar enabled in iconbar #270 Already closed as solved.