Proposed

tree_proc(id_panel, id_operation, item, index, text, icon)

Controls tree panel.

Possible values of id_panel:

Possible values of id_operation:

TREE_ITEM_ENUM: Enumerates subitems of item. Param item. Gets list of subitem handles.
TREE_ITEM_ADD: Adds subitem as item's child. Param item. Param index: at which subitem index to insert (0..child_count-1), or -1 to append. Param text: caption of item. Param icon: index in imagelist or -1.
TREE_ITEM_DELETE: Deletes item (with all subitems). Param item.
TREE_ITEM_SET_NAME: Sets new item name. Params: item, text.
TREE_ITEM_SET_ICON: Sets new item icon. Params: item, icon: index in imagelist.
TREE_ICON_ADD: Adds icon to imagelist. Param text: path to png file. Gets imagelist index of new icon.
TREE_ICON_DELETE: Deletes icon from imagelist (note: icons after this imagelist index will shift, will have new imagelist index). Param icon: index in imagelist (0..count-1). Gets bool: index existed before.

Param item can be 0 for invisible root-item, e.g. you can clear tree if use root-item.

App-proc

PROC_SIDEPANEL_ADD: Adds tab+control to sidebar. Text is ","-separated params: caption of panel, tab index (0-based, -1 to add tab to end), type of control. Type of control allowed: "tree", "list". Gets bool: params ok, tab was added.
PROC_SIDEPANEL_ACTIVATE: Activates tab in sidebar. Text is caption of tab. Gets bool: tab found/activated.
PROC_SIDEPANEL_ENUM: Gets str, "\n"-separated tab captions.
PROC_SIDEPANEL_GET_CONTROL: Gets int handle of control, associated with tab. Text is caption of tab. Gets None if cannot find tab.