Hello H,
Thanks for your comments and suggestions.
Regarding the issue with limited accounts, we believe we have that issue fixed in our latest version (1.4.0). The problem with earlier versions is that the default user database folder was in the application folder, which limited users do not have access to. In version 1.4.0 (and later versions) the default user database path is in 'My Documents\Work Time Studio\Database', where all users, including limited users, have access to. I'd encourage you to download the latest version and give it a try. I think it'll resolve this issue. You'll have a full 30 days of trial with the new version, regardless of the number of days you have been trying the previous version.

You have a good list of features that you'd like to see in you're ideal tool. I feel that in it's current state, Work Time Studio meets most of these criteria. I'll discuss this below.
1. refine their tree structures by introducing more categories (like purpose, visions, goals, etc.)
Work Time Studio allows you to create your own
WorkItem Types, which I think you refer to as categories. As far as we know, Work Time Studio is the only software application in it's class to provide this feature. The context help discusses WorkItem Types in much detail, and how you can create your own types for the specific nature of your work.
2. to sort each item in each level (Purposes, Visions, Goals, Projects, Tasks) by order of importance - from the most important at the top to the least important at the bottom, using drag and drop if possible (more ergonomic),
This is the purpose of the
Prioritizer. We wanted to give users this ability in a different window than the Activity Tree, as to not take away the purpose and hierarchal benefits of the Activity Tree. We have recently added more functionality to the Prioritizer, since it's so important. Now, you can drag and drop WorkItems listed in the Prioritizer right to the Activity Calendar, to schedule a time you wish to work on the specific WorkItem.
3. to assign to each item in each level a priority, using ABC123 or a scale with a clear specific index, using drag and drop if possible (more ergonomic).
This is currently possible in the Activity Tree, where WorkItems are entered. Along with assigning a level of priority, you can also assign a level of difficulty, a status, and an estimated time for the WorkItem. These properties are then used in the Prioritizer to sort the prioritized list based on the importance you give to each of the properties.
4. I would also need a feature enabling me to assign, on a daily, weekly, monthly or yearly basis, a specific amount of time per vision, per goal, per project, per value, per role, etc. In other words, I should, ideally speaking, devote a certain amount of time to making progress towards a certain vision, goal, project, value, role etc. WTS would then enable me to check whether the sum of time I am using on the tasks I have scheduled for the next day, week, month or year is less than, equals or is more than the amount of time I should ideally devote to a vision, a goal, etc.
Because of the hierarchal features built into the Activity Tree, Work Time Studio can allow you to track or limit your estimated, allocated, or actual time on tasks (leaf WorkItems) as well as projects or goals (branch WorkItems). All WorkItems have a property called 'Collective Estimated Time' and 'Collective Actual Time'. These properties show the total amount of time from all their descendants, so it's easy to see at a glance the overall picture and progress of a project or goal. Plus, these properties are updated in real-time as you work on tasks that are descendants of those projects or goals.
5. I wish WTS could fully synchronize with Outlook, since most smartphones are designed to sync with it.
We hear you there. We hope to have export and import capabilities, as well as synchronize capabilities added to Work Time Studio in the next couple releases.
If I mis-understood any of the ideas you had in any of the above, feel free to correct me. I may not be visualizing the ideas you're presenting properly. I appreciate your input!