I'm using the latest nightly build for mac and audio columns inside a subxsheet can be heard outside the subxsheet.
Consider using one audio file that runs the length of your scene with all relevant sounds included in that one audio file instead of multiple files or collapse all your audio into a subxsheet so that all your audio plays in one column starting on frame 1. if you've timed out your scene, with an animatic for instance, you should be able to load one audio file in on frame 1 regardless of being on the main timeline or in a subxsheet and everything will line up. loading audio into multiple subsheets just involves copying the columns and pasting the column and should only take a heartbeat to accomplish, commandC then commandV.
Whether you connect the columns yourself in the schematic window, use the skeleton tool in the combo viewer, or don't rig anything at all, it doesn't change the functionality I'm talking about with the skeleton tool. clicking on a drawing in the combo viewer using the skeleton tool moves the selected column to the column containing the drawing you clicked AND moves the xsheet so that that column is visible in the xsheet. so say you have 5 characters and a bunch background elements in your scene spread across 250 columns, no matter what column youre on, if you click character A's hand (which is on column 150) with the skeleton tool, you have just selected column 150 to edit and have moved the focus of the xsheet so that you're looking at column 150. Then clicking a bush in the background stored on column 6, means you're now working on column 6 and opentoonz automatically scrolls along the xsheet so that you're looking at column 6 in the xsheet.
no need to scroll through the xsheet yourself looking at column names or column images guessing which column holds which drawings, just click the drawing in the combo viewer with the skeleton tool.