Maintenance of unofficial tracks

In the national park near to where I live (blue mountains) there are a number of historic tracks that are not officially maintained. The canonical example of this is the Lindeman Pass, constructed in the early 20th century, never officially opened, fell into disrepute, then was recut and publicized by Jim Smith and others in the 1980s. Some sections of this are very clear, other parts though are quite overgrown, including some of the access tracks that connect to the Lindeman from the top of the escarpment.
I am interested to hear people's views on the ethics and legality of maintaining these tracks. Eg some or all of
- tying ribbons and/or nailing markers to trees
- removing dead trees and branches from the track
- pruning branches on living trees that are blocking the existing path
- pruning branches on living trees that are not yet blocking the path, but would if left unchecked
- cutting a new section of a track through the bush where the original has been overgrown and lost, or else blocked due to landslide or an obstacle that is too big to move.
I am interested to hear people's views on the ethics and legality of maintaining these tracks. Eg some or all of
- tying ribbons and/or nailing markers to trees
- removing dead trees and branches from the track
- pruning branches on living trees that are blocking the existing path
- pruning branches on living trees that are not yet blocking the path, but would if left unchecked
- cutting a new section of a track through the bush where the original has been overgrown and lost, or else blocked due to landslide or an obstacle that is too big to move.