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When you install on Linux (Ubuntu) the Firefox, for default, the bookmark icon is not present in the first line of your browser, see below.
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For see the bookmark in the first line, like below, see the our explanation.
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Click the menu button:
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Now click on: MORE TOOLS
and next click on: CUSTOMIZE TOOLBAR
and now drag and drop the tool that you need present on the first line, see example below.
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Now you must see the below configuration.
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