Using a custom roadmap with the main object of initiatives and with the setting of compact bars enabled, still doesn't make the roadmap items as compact as it could. See the image below. There is one extra line item on its own that could be moved next to a horizontal space that already exists.
By default the labels on bars will float as you scroll the roadmap horizontally. This to to allow you to view the entire label even if the bar is only partially visible. However, you can override this behavior by unchecking the Labels on scroll setting. This will allow bars to fit next to each other in a more compact fashion (exactly as is requested in the screenshot linked in the comment.)
With other roadmapping tools I have always been able to create a continuous progression of work on a single row, as our teams flow from one initiative/feature to another. The "compact" version of the roadmap should be just that, compact, and currently it is not. I can't capture my full roadmap in one screen like I should be able to because of this buffer requirement. It not only takes too much space, it doesn't show the continuation from one set of work to another as it should for that row. (your 'Attach files' prompt does not appear to be working in this interaction) Screen shot