One of the things I like about physical story boards is that they're more compact visually because the increment lines are not forced to be strictly a horizontal line. They can be drawn between the subtasks with vertical connectors between each column, eliminating the need for all the empty space created when columns have an uneven number of subtasks in the columns. As a first increment, you could create that option just for visualization purposes in the JPG export and see what people think of it. Ideally it would be an available view in the working space. I'd be happy to provide a visual/picture if there is a way for me to submit it.

I try to thin slice my User Stories. That means that some of my User Stories are sequential tasks or journey points.

Currently I can, under a Yellow Card on the second level, put Stories one after the other on the third level in vertical columns. But I can't create a vertical layout to map stories "link" between columns.

Ability to have side cards like the yellow card is very important for the third level.

Because most likely one story will be just before another or may be actually in same level.

For example, "Online Paying" can be with Visa or MasterCard or Amex. I would like to have those 3 Paying Story on the same vertical row.

Creating yellow columns for this need would work if I had only one vertical, but if I have multiple verticals of various width, then I would not be able to do it efficiently.

Ability to have side cards for the third level, so I would have Feature - Epic - Multiple Stories horizontally mapped. That means that the first and second level would span horizontal also (or at least keep same size but next sibling card would be at the end of the "span")

When pressing ESC when editing a user story, save the current state of the story.

I often enter some details for a story, then think about editing another one. I then press ESC to close the screen I'm currently in and switch to another one, only to discover that pressing ESC resulted in the loss of all the entered information.

Although I understand that pressing ESC to save information feels a bit strange, it would be great if pressing ESC atleast does not result in the direct loss of information.

Alternatively a popup informing you that you'll lose your information would help.