Default Hotkeys:

Alt+Shift+Left: Move tab one to the left, wrapping to the right end if the tab is currently in the first position
Alt+Shift+Right: Move tab one to the right, wrapping to the left end if the tab is currently in the last position
Alt+Shift+0: Move tab to the start of the tab bar
Alt+Shift+9: Move tab to the end of the tab bar

The hotkeys for those actions can be changed on the Options page. Multi-Selected Tabs: Starting with Firefox 63, if you enable the browser.tabs.multiselect in about:config, you can select multiple tabs at a time. If this feature is turned on, the tabs can be moved as a group. This can be turned off on the Options page if you prefer to only move the current tab even when others are selected. Notes on Pinned Tabs:

If you have any pinned tabs, pinned tabs and non-pinned tabs are treated like separate tab bars. Non-pinned tabs move to start/end of the non-pinned tabs section.
If multiple tab selection is enabled and you select a group containing both pinned and non-pinned tabs, no movement will be possible.