It is a very important question for me as well. The only way I could do was to insert a line (with arrow end) and overlap to the axis. For specific question related to Veusz, perhaps you can join and ask in the Veusz forum which is quite responsive and helpful. Veusz discussion subreddit
It is a very important question for me as well. The only way I could do was to insert a line (with arrow end) and overlap to the axis. For specific question related to Veusz, perhaps you can join and ask in the Veusz forum which is quite responsive and helpful. Veusz discussion subreddit