@visualrevolt Hi, and welcome to VectorStyler.
Some of these are doable, but maybe later (after 1.2):
B-Spline tool
Yes, this is in the backlog (but after 1.2). There is a Smooth Nodes option in the context panel for the Pen tool. Not the same as b-spline, but can click+create smooth curves.
Page manager
Was not planning this in the roadmap for now.
There is the Canvas & Artboard panel but without previews.
To preview an artboard, longpress with the mouse on the artboard icon.
Group/ Ungroup tab
There is in the roadmap a context sensitive / customizable command popover menu, but this is further down the road.
Navigation bar
There is the navigator panel, and then the zoom / pan / rotate tools at the bottom of the toolbox.
Maybe having some of these tools into the status bar (bottom row of the window) could be added.
Collapsible Side Panels
Added this to the backlog. There is a plan to have panels collapsed to icons.
Tool Tabs
This is possible already. Just drag the tool group popover from its title knob (vertical line on the left), and place it anywhere on the screen, or dock it on the side.
BTW: many of the vertical panels (like Transform, Stroke, etc) can be docked horizontally also, where they change layout.