I am interested in creating a live USB for a Linux distribution (Tails preferred). But, with customized software already installed, such as a specific web browser with pre-existing bookmarks stuff such as that.
I have seen some discussions about this and even some tools which claim they can do it. But, in looking at the features, it is not clear if they actually can.
What would be the best way to go about doing this?
I had a try at this (see the lumina desktop posts). It is not easy. There is no off the shelf software to do it.
There are two ways
make a bootable .iso file and put it on the usb drive. This will not be writeable, so you cannot make changes., unless you use special techniques to make what is called permanence. Making iso files is difficult because every distro is different. There is no general method.
do a full linux install of your custom linux on the usb drive, and add grub to make it bootable. This will be writeable, like any full install, and will be larger than the corresponding iso file because it is not compressed. Making a full install is easy.
So decide which you want. If it is the latter, I can help with a fully documented method.
Regards
Neville
Again, I have had a total 
meidiot (not sure this word is Linux) issues with USB; to mount or to un-mount and if so when? Then I decided to add the KDE experience and my USB seem to mount but…did I need to un-mount, I didn’t know? Learning curve again, USB has partitions I did not realize and I probably should have been un-mounting. In Ubuntu-Gnome, I just depended on the “safe to remove” factor, never experiencing a problem, at least not one I knew about 
.
So with the “lessons learned- newbie”; I had an older Lexar USB that I could not format until I went into “disks and partitions”, there I was able to format and delete old files from the Lexar! (So excited; finally did something on my own that worked).
I then downloaded Belena-etcher (used this before), went to the Manjaro websight to find many desktops I could have, I chose; the Xfce, it looked like my “speed”. Once it downloaded, Belena-etcher did all the rest. Now, in my possession is a boot-able disk and I am using Manjaro.
This is likely not an answer for anyone but I gave it a shot. Not having enough time to “read”, practice and Learn Linux, Manjaro seems like a Beginners kind of desktop and I am starting this Linux life all over again!
Thank you’s go to Neville and Daniel who have helped me along the journey thru my 
unknown-Ubuntu. Trust the input that these 2 give!